If you say it in January, they will ;) Otherwise, probably not, although in my experience it's more common to say "Happy Fourth of July." Independence Day isn't associated as strongly with a greeting as other holidays are, so while it's quite common to say "Merry Christmas", wishing someone a happy Independence Day isn't as common.

No, I do not think anyone would be embarrassed. They might feel a little complimented.

Not at all. It is every 4th of July and you can wish someone ' Happy 4th of July '.

I agree with Susan. Although, when someone said Happy 4th of July to me here in the Netherlands, I felt confused, because it's not something you hear often. People don't usually wish each other a happy 4th of July.